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TheOriginoftheElementsTheBigBangThenucleosynthesisoflightelementsThenucleosynthesisofheavyelements

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TheBigBang

Theory

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TheBigBangTheory

Ouruniverseisthoughttohavebegunasaninfinitelysmall,infinitelyhot,infinitelydense

somethingasingularity

Ini=altemperatureimmediatelya?ertheBigBang~109K

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TheBigBangTheory

Fundamentalpar=clesproducedintheexplosionhadtoomuchkine=cenergyto

bindtogether

Thentheuniversestartedtodecreaseintemperature

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TheBigBangTheory

Thepar=clesmovedmoreslowlyandsoonbegantoadheretogether

Influencedbyavarietyofforces:STRONGFORCEandELECTROMAGNETICFORCE

SpacebeganinsideofthesingularityandTheBigBangisthebeginningoftheEXPANSIONofspace

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TheBigBangTheory

StrongForceShort-rangebutpowerfulaVrac=veforce

betweenprotons,neutronsandeachother

---boundpar=cletogetherintonuclei

Electromagne/cForceRela=velyweakbutlong-rangeforcebetweenelectriccharges---boundelectronstonucleito

formatoms

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Review:IsotopicNota=on

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The

Nucleosynthesis

ofLightElements

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BigBangNucleosynthesis:HandHe

+H1

1n

0

1H

1

2

+H1

2n

0

1H

1

3

He2

3He

2

4+ n

0

1

+H1

2H

1

1He

2

3

+H13 H

11 He

24

He-4 is very stablecompared to other light

nuclei.

Almost all neutronscombine with protons to

form He-4.

Happened at the core ofthe star

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He2

4

He2

5

+ H1

1

+ n0

1

He2

4

Li3

5He

2

4

+He2

4Be

4

8

BBNceasesatHe-4becausenostablenucleiare

producedbythefollowingreac=ons:

UnstablebecauseanyLi,BeorBformedgoesontoreactwith

morealphapar:cles

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Heliumburning

ExplainsthelowabundanceofLi,BeandB

Energyisreleasedwhenlightnucleifusetogethertogiveelementsofhigheratomicnumber

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Nuclearburning

Elementsofatomicnumberupto26wereformed Suchelementsaretheproductsofthenuclearfusionevents---nuclearburning

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WhydoesfusionstopatFe

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NuclearBindingEnergy

theenergyrequiredtobreakdownanucleusintoitscomponentnucleons

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Nuclear Binding Energy vs Atomic Mass

Fusion of light nuclei produces more stablenuclei (higher nuclear binding energy); energy

is released

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Nuclear Binding Energy vs Atomic Mass

Fe-56 is at the top of the curve; point ofmaximum stability occurs around Fe-56

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Nuclear Binding Energy vs Atomic Mass

Fusion of iron nuclei requires energy.

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WhydoesfusionstopatFe

Fe with 26 protons is at the top of the BindingEnergy vs Mass No. curve

Fusion of Fe nuclei REQUIRES energy, insteadof emitting energy

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The

Nucleosynthesis

ofHeavyElements

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SynthesisofelementsheavierthanIron

Produced by a variety of energy-consumingprocesses

Requires a different mechanism --- NOT by nuclearFUSION at the core of the stars

Heavier elements are produced duringSUPERNOVA explosions --- condition of intense

neutron flux

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SUPERNOA:explodingstar

Fusion stops Core collapses

Temperature goes up butdoes not stop collapse

Protons and electrons combine toproduce neutrons

density at center > density of a nucleus

THESTARBLOWSAPART!

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Agivennucleusmaycaptureasuccessionofneutronsandbecomeprogressivelyheavierisotope

Thentherecomesapointatwhichitwillejectanelectronfromthenucleusasapar=cle

SynthesisofelementsheavierthanIron

daughternuclide

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SUMMARY

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TheBigBang

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Fusion STOPS

H fusion He

He fusion C (O)

C fusion Ne, Mg

Ne fusion S

O fusion Si

Si, S fusion Fe

7 million years

500 000 years

600 years

1 year

6 months

1 day

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SUPERNOAEXPLOSION

Fusion STOPS

SYNTHESISOFHEAYELEMENTS

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OtherResources

TheElements:ForgedinStars

hVp://www.youtube.com/watch

vuKqvjEE0wFg&featurerelated

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END